A cellular phone with a camera including a digital camera has been spread. A cellular phone with a camera of a background art uses an image taking lens having a single focus and an image sensor having a low resolution for small-sized formation and a reduction in cost. However, there are a number of users requesting a high image quality image taking function for a cellular phone with a camera and therefore, in recent years, a cellular phone with a camera using optical zooming and automatic focusing, an image sensor having a large number of pixels or the like is also on sale.
A zoom lens apparatus needs a minimum of two lens groups movable in an optical axis direction. Further, there is needed a lens driving mechanism capable of individually moving respective lens groups in zoom adjusting, moving only one lens group in adjusting focus, or moving two lens groups in the same direction and by the same amount. A digital camera integrated to a cellular phone with a camera is very small-sized and therefore, a zoom lens apparatus of a lens barrel type which needs to form a fine cam groove at an outer periphery thereof cannot be used. Further, a zoom lens apparatus of an outer zoom type in which a lens barrel is extracted to outside of a cellular phone with a camera by zoom adjusting is not suitable for a cellular phone with a camera which is frequently handled roughly.
Hence, a cellular phone with a camera having optical zoom of a background art uses a lens driving mechanism of an inner zoom type attaching nuts to two lens groups held to be movable in an optical axis direction, and screwing feed screws in a rod-like shape to the nuts and rotating the feed screws by a motor. However, when two lens driving mechanisms are integrated for zooming and focusing, an influence on a size and cost of the cellular phone with a camera is considerable.
In order to constitute a camera by a small-sized formation and low cost formation, a zoom lens capable of adjusting zooming and focusing by a single lens driving mechanism has been invented. For example, according to a zoom lens apparatus described in JP-A-11-064708, a cam ring rotated at an outer periphery of a fixed cylinder is formed with two pieces of cam grooves inserted with cam followers of two pieces of lens groups integrated to inside of the fixed cylinder, a width of one cam groove thereof is made to be wider than that of the other. In rotating the cam ring in one direction, the respective lens groups are moved in an optical axis direction by the respective cam grooves to perform zoom adjusting. When the cam ring is rotated in other direction, the lens group engaged with the cam groove having a narrow width follows the cam groove to move, the lens group engaged with the cam groove having the wide width is not moved until the cam groove is brought into contact with the cam follower and therefore, focus adjusting is performed in a state in which a zoom magnification is not varied.
Further, according to a zoom lens apparatus described in JP-A-09-049958, there is provided an engageable and disengageable rotation transmitting mechanism between a middle cylinder for moving a front group lens by rotation and a cam cylinder provided coaxially with the middle cylinder for moving a rear group lens for executing zoom adjusting by rotating both of the middle cylinder and the cam cylinder when engaged and for executing focus adjusting by stopping to rotate the cam cylinder and rotating only the middle cylinder over a predetermined angular range when not engaged.
According to the zoom lens apparatus described in JP-A-11-064708 and JP-A-09-049958, the single piece of motor can be used both for zoom adjusting and focus adjusting and therefore, the apparatus can contribute to small-sized formation and low cost formation of the cellular phone with a camera. However, both of the apparatus are of the outer zoom type using the lens barrel and extracting the lens barrel to a front side in zoom adjusting and therefore, the apparatus are not suitable for the cellular phone with a camera.